The outbreak of Ebola disease caused by Bundibugyo virus in the Democratic Republic of the Congo had reached 5,290 confirmed cases and 2,516 deaths as of 19 August, according to the epidemiological update published by the European Centre for Disease Prevention and Control on 21 August. A further 1,152 people had recovered and 837 remained in isolation care.
The figures are provisional and have been revised in both directions as cases are reclassified. The World Health Organization’s Disease Outbreak News of 14 August recorded 4,665 confirmed cases and 2,184 deaths as of 12 August, and put the case fatality ratio in the DRC at 46.8 per cent. The difference between the two counts is one of reporting date and case definition rather than disagreement; the direction of travel is not in doubt.
Ituri province remains the centre of it, with 4,447 cases and 1,984 deaths recorded across 28 of its 36 health zones. The outbreak was first detected in May and now touches six provinces. In its rapid risk assessment of 20 August the WHO kept the risk to the DRC at “very high” and to neighbouring countries at “high,” while assessing the global risk as low, and noted that many transmission chains remain unidentified. Imported cases have been recorded in Uganda, France and Germany without sustained onward transmission.
The particular difficulty is the virus itself. Bundibugyo is a distinct species within the same genus as Zaire ebolavirus, and no vaccine is licensed against it. On 20 August the International Coordinating Group on Vaccine Provision allocated 70,000 doses of Ervebo — the Zaire-strain vaccine — to the DRC: 20,000 for a phase 3 trial to test whether it protects against Bundibugyo at all, and 50,000 for frontline and health workers. Among the latter the toll has already been heavy: WHO recorded at least 155 confirmed infections among health workers, including 45 deaths, as of 9 August.
The trial is, in effect, both a research question and the response itself.